This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
In the current 3GPP standard, TS 23.401 version 8.3.0, it is specified that the Serving GW shall generate an “end marker” packet, see FIG. 1, to assist the target eNodeB to perform reordering of downlink packets to the UE. FIG. 1 shows handover without serving GW relocation.
1. The target eNodeB sends a Path Switch Request message to MME to inform that the UE has changed cell, including the ECGI of the target cell and the list of rejected EPS bearers. The MME determines that the Serving GW can continue to serve the UE
2. The MME sends a User Plane Update Request (eNodeB address(es) and TEIDs for downlink user plane for the accepted EPS bearers) message to the Serving GW.
In case any EPS bearers are to be released the MME triggers the bearer release procedure as specified in clause 5.4.4.2.
3. The Serving GW starts sending downlink packets to the target eNodeB using the newly received address and TEIDs. A User Plane Update Response message is sent back to the MME.
4. In order to assist the reordering function in the target eNB, the Serving GW shall send one or more “end marker” packets on the old path immediately after switching the path as defined in TS 36.300 [5], clause 10.1.2.2.
In the EPS, it is also possible to have the target RAN, e.g. target eNodeB, connected to a target Serving GW, see FIG. 2. During the handover procedure the Serving GWs must also be changed. This means the “end marker” packets generation by the current solution will not work correctly. In fact no “end marker” will be generated in case of Serving GW relocation. FIG. 2 shows handover with serving GW relocation.